1. Field of the Invention
The present invention relates to an organic electroluminescent device, and more particularly, to an organic electroluminescent (EL) device comprising a structure having an anode, an emitting layer, and a cathode stacked therein, wherein a fluorescent compound of Formula 1 is used as a emitting material of the emitting layer of the EL device, or used as a dopant of the emitting layer of the EL device, a fluorescent compound of Formula 1 is used as a dopant and a fluorescent compound of Formula 2 is used as a host of the emitting layer of the EL device.
Recently, an increase in sizes of displays has raised an increasing need for flat-panel displays taking up a small space. There have been rapid developments in the technology of organic electroluminescent (EL) devices, also called organic light emitting diodes (OLEDs), among these including flat-panel displays, and various pilot products thereof have already been released.
2. Discussion of the Related Art
An organic electroluminescent (EL) device is a system that emits light when electrons recombine with holes to thereby form electron-hole pairs and then they disappear, via injection of electric charges into an organic film formed between an electron-injection electrode (cathode) and a hole-injection electrode (anode). The organic electroluminescent device exhibits advantages such as capability to fabricate the device on a flexible and transparent substrate such as plastic materials, capability to operate at a lower voltage (less than 10 volts) compared to plasma display panels or inorganic EL displays, relatively low consumption of electric power, and superior tunability of colors of emitting light to desired colors. In addition, organic EL devices can display light of three colors, i.e., green, blue and red light, and thus have been receiving a great deal of attention as a next generation of displays capable of emitting various colors.
A method for fabricating a conventional organic EL device will be briefly reviewed as follows.
First, an anode material is deposited on a transparent substrate. As the anode material, indium tin oxide (ITO) is commonly used.
Next, a hole-injection layer (HIL) is deposited thereon. As the hole-injection layer, copper phthalocyanine (CuPc) is usually deposited to a thickness of 10 to 30 nm on the anode.
Next, a hole-transport layer (HTL) is deposited on the hole-injection layer. 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), as the hole-transport layer (HTL), is deposited to a thickness of 30 to 60 nm on the hole-injection layer.
An organic emitting layer is then formed on the hole-transport layer. Herein, if necessary, a dopant may be added to the organic emitting layer. For example, if it is desired to fabricate the organic EL device emitting green light, tris(8-hydroxy-quinolate)aluminum (hereinafter, referred to simply as Alq3) as the organic emitting layer is deposited to a thickness of about 30 to 60 nm. Herein, N-methylquinacridone (MQD) is primarily employed as the dopant.
Then, an electron-transport layer (ETL) and an electron-injection layer (EIL) are sequentially deposited on the organic emitting layer, or otherwise an electron-injection/transport layer is formed thereon. If it is desired to emit green light, an electron-injection layer (EIL)/electron-transport layer (ETL) may not necessary because Alq3 used for the organic emitting layer has high electron-transporting ability.
Then, a cathode is formed thereon and finally, a protective film is additionally coated on the resulting structure.
Depending upon how the emitting layer is formed in the resulting structure, it is possible to fabricate a blue-, green- or red-emitting device as desired. Meanwhile, materials used as emitting compounds to realize conventional emitting devices have suffered from problems associated with poor operating lifetime and luminous efficiency.